Final answer:
In a negative feedback loop, the effector acts to return a physiological variable to its normal range. This component responds to directives from the control center to address imbalances and maintain homeostasis.
Step-by-step explanation:
In a negative feedback loop, the portion that brings the system back to its normal value is the effector. It is an integral component of a homeostatic control mechanism, acting upon the directions from the control center to adjust the variable back toward a set point. This type of feedback is crucial for maintaining stability within biological systems by counteracting any deviation from an organism's normal functioning state.
For instance, in the regulation of body temperature, when the body temperature rises above the normal range, the effectors, which could be sweat glands or blood vessels, are activated by the control center to dissipate excess heat and bring the temperature down to a normal level. Similarly, in blood glucose control, when glucose levels are too high, effectors such as the pancreas release insulin to help lower the glucose back to a stable level. These examples illustrate the vital role of the effector in the negative feedback process to ensure the body remains in equilibrium.